The region had managed to avoid the disease that this summer has been the worst since it was first detected in the U.S. in 1999. Statewide, 11 cases have been confirmed, with one death. The increase in West Nile cases nationally is thought to be due to unusually warm weather.

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The county said many people who contract the virus don't know they have it and thus don't report it because 80 percent experience no symptoms. Up to 20 percent develop mild symptoms including fever, headaches, body aches and possibly a skin rash or swollen lymph glands.

However, the county said about one in 150 people infected with West Nile will experience more serious illness and sometimes death, usually in older adults.

The county health department encouraged residents to protect themselves while outside by using mosquito repellent and wearing long pants and long sleeves, especially during dawn and dusk when mosquitoes are most active. Mosquito populations aren't markedly reduced until the first hard frost, the county said.